1. Field of the Invention
The present invention relates to a liquid crystal display device using backlight light together with ambient light to provide a display.
2. Description of the Related Art
In recent years, liquid crystal display devices are applied to various fields of notebook personal computers, monitors, car navigations, mid- or small-size TV, portable telephones and the like. Among them, a reflection type liquid crystal display device does not require a backlight, and therefore, application thereof to a display for a mobile equipment such as a mobile PC or the like is studied to make use of an advantage of low power consumption, thinness and lightness.
Since the reflection type liquid crystal display device provides a display by utilizing ambient light, the brightness of a display screen depends on the illumination environment surrounding the display screen like paper. Particularly, nothing can be observed in a dark place. Therefore, recently, a liquid crystal display device which auxiliary utilizes an internal light source in dark illumination environment steps into the limelight. Such a liquid crystal display device is known, for example, as a semi-transmission type liquid crystal display device having a backlight which is an internal light source disposed behind a display screen or a reflection type liquid crystal display device having a front-light which is an internal light source disposed in front of a display screen.
By the way, in order to improve thinness and lightness while the power consumption is reduced in either of the liquid crystal display devices, it is necessary to enhance the light utilization efficiency as highly as possible. For this purpose, various improvement measures relating to optical films and liquid crystal modes are proposed. For example, Jap. Pat. Appln. KOKAI Publication No. 11-242226 discloses a semi-transmission type liquid crystal display device which enhances the light utilization efficiency by making different cell gaps between transmission regions and reflection regions obtained by dividing each pixel and utilizing a homogeneous mode.
However, the above improvement measures cannot make it possible to attain a sufficient viewing angle characteristic when the display device is viewed from an orientation or direction other than the front. That is, there occurs a problem that coloring becomes unnatural, the contrast is lowered or display of black and white is reversed. In order to solve the problem of viewing angle characteristic, a large number of methods for adding a viewing angle compensation film are proposed, for example, in Jap. Pat. Appln. KOKAI Publication No. 2000-258769. However, the conventional viewing angle compensation system has a large number of problems that the compensation effect is not sufficient, the cost becomes extremely high by using a plurality of expensive films, and at the same time, the thickness and weight of the liquid crystal display device are increased and mass production is difficult to attain because films which cannot be formed by a simple manufacturing process are used, for example.